Interesting question!
There are a lot of possible explanations:
1. If you've logged mobile WiFi access points, things you've observed may have been more commonly seen elsewhere. If you pick an individual point, you can look it up in the detail search to get a coverage polygon.
2. If an access point has moved, we try and make it "skip" from location to location, but this cluster detection is still somewhat rudimentary, and things can "smear" if a lot of conflicting observations have been recorded (check out the smudges in central Africa, over parts of western Asia, or between a lot of major cities in the US and EU). This happens with APs that are commonly seen in two or more different places (someone takes their network to their vacation home), or if someone's car-based AP migrates through the same route frequently and gets observed.
3. If you have GPS malfunctions (as many android handsets quietly do), you'll often observe radial lines from the actual location of the AP. This happens when the GPS reports high accuracy, but actually has a bad fix.
4. If you stumble while onboard a plane, things get weird fast. Plane based observations often cluster around "great circles" so if you see radial lines that follow a uniform "arc" from airport to airport on the map instead of a linear route, this is probably real wifi instead of buggy GPS.

Each of these has different failure modes - tell us a little more about the type of spots you're seeing and their location?

Example... I have never been to Seattle WA. Yet there are over a dozen spots showing when I am filtering on "Only discovered by me"
I guess what caught me off guard was I was moving the map around and noticed a few areas with purple that I had never been to.

That coverage polygon is cool. Would like to learn more if there are other features to search / mapping like that.Is there a howto use map searches and what clicks do to results?

Examples:
PJ-673_5105 which is ad-hoc 8a:5a:d3:13:18:28 yeah since ad-hoc could be floating around.

MB Hotspot 4641545 ac:7a:4d:ed:37:ba this looks like its moved around too...

WiFi Hotspot 1072 78:61:7c:65:44:02 this one is showing its jumped around over time as well.

So after doing my homework, it does appear that this tiny sampling are things that have moved. I must have enough finds, that when i move around the map, devices have moved since I discovered them. Very interesting, never really thought about it before.

I'm experiencing the same phenomenon. I've never been to Seattle, Salt Lake City, Kansas City, or Los Angeles but I have groupings of points in all of these cities. All of the other groupings are legit. I'm not really concerned about it but just bewildered.

WiGLE respects your privacy. To have records of your access point removed from our database, or if you have any questions or suggestions, send an email to: WiGLE-admin[at]WiGLE.net
(please include BSSID (MAC) in removal requests). We're also on IRC: at WiGLE.net:6667